1. Field of the Invention
The present invention relates to a socket for an electrical part which is mounted on a wiring substrate and accommodates an electrical part such as a semiconductor device (hereinafter called “IC package”) for performing a test of the electrical part, for example.
2. Description of the Prior Art
In a known art, there has been provided an IC socket as “a socket for an electrical part” for accommodating and detachably holding an IC package as an “electrical part” (see Japanese patent Gazette No. 3566691).
The IC package comprises a package body (i.e. an electrical part body), the shape of which is a square for example, and the package body is provided with the terminals.
On the other hand, the IC socket comprises a socket body which is mounted on a wiring substrate, and the socket body comprises a contact pin unit provided with plural contact pins for electrically connecting the terminals of the IC package and the wiring substrate.
In addition, a floating plate is mounted in the socket body so as to be capable of moving vertically under the state that the floating plate is urged upward by a spring. The IC socket is constituted so that the IC package is accommodated on the floating plate.
When the IC socket is mounted on the wiring substrate and used, the IC package is accommodated on the floating plate and is pressed from the upper side, consequently, the floating plate moves downward.
Then, the upper side contact portions of the contact pins are pressed onto the terminals of the IC package via the through holes formed in the floating plate, simultaneously, the lower side contact portions of the contact pins are pressed onto the electrode of the wiring substrate.
Under such condition, the electric current is supplied from the wiring substrate to the IC package through the contact pins, then, the burn-in test or other kind of test is performed.
However, in the case such a conventional IC socket is used, the floating plate is positioned at the upper side because of the urging of the spring, when the IC socket is carried under the state that the IC socket is not yet mounted on the wiring substrate. Therefore, the upper side contact portions are possible to come out from the through holes of the floating plate, if the contact pins are too short and the upper side contact portions of them do not deeply enter the through holes.
If the IC socket is mounted on the wiring substrate and used under such state, there is a possibility that any defects, such as collision between lower surface of the floating plate and the upper side contact portion, occur when the floating plate is moved downward.